Crown and leaf traits as predictors of subtropical tree sapling growth rates

Aims Growth rates of plants are driven by factors that influence the amount of resources captured and the efficiency of resource use.In trees,the amount of light captured and the efficiency of light use strongly depends on crown characteristics and leaf traits.Although theory predicts that both crown and leaf traits affect tree growth,few studies have yet to integrate these two types of traits to explain species-specific growth rates.Using 37 broad-leaved tree species of subtropical forests in SE China,we investigated how interspecific differences in wood volume growth rates were affected by crown and leaf traits.We tested the hypotheses that(i)larger crown dimensions promote growth rates,(ii)species-specific growth rates are positively related to leaf stomatal conductance,leaf water potential and leaf chemical components,and negatively related to leaf C/N and leaf toughness and(iii)the two sets of traits better explain growth rates in combination than either alone.Methods Our study was conducted in a large-scale forest Biodiversity and Ecosystem Functioning experiment in China(BEF-China),located in a mountainous region in Jiangxi Province.We related 17 functional traits(two crown dimension and three crown structure traits;six physiological and six morphological leaf traits)to the mean annual growth rate of wood volume of young trees of the studied species.Interrelationships between crown and leaf traits were analyzed using principal component analysis.Simple linear regression analysis was used to test the effect of each trait separately.We used multiple regression analysis to establish the relationship of growth rate to each set of traits(crown traits,physiological and morphological leaf traits)and to the combination of all types of traits.The coefficients of determination(R^(2)_(adj))of the best multiple regression models were compared to determine the relative explanatory power of crown and leaf traits and a combination of both.Important Findings The species-specific growth rates were not related to any of the single crown traits,but were related positively to leaf stomatal conductance and leaf water potential individually,and negatively to leaf toughness,with approximately 13%variance explained by each of the traits.Combinations of different crown traits did not significantly explain the species-specific growth rates,whereas combinations of either physiological or morphological leaf traits explained 24%and 31%,respectively.A combination of both crown and leaf traits explained 42%of variance in species-specific growth rates.We concluded that sets of traits related to carbon assimilation at the leaf-level and to overall amount of leaves exposed at the crown-level jointly explained species-specific growth rates better than either set of traits alone.

Diverse plant mixtures sustain a greater arbuscular mycorrhizal fungi spore viability than monocultures after 12 years

密集的土地管理可能损害土壤生物多样性,从而危害长期的土壤生产力。丛枝菌根真菌(AMF)通过与植物专一性的共生关系,在促进土壤生产力方面发挥着关键作用。然而,目前尚不清楚植物群落的性质,特别是植物物种丰富度和组成如何影响土壤中AMF种群的生存能力。本研究中,我们测试了来自不同植物功能类群的8种植物的单一栽培和不同植物的混合种植,是否可以维持更有活力的AMF繁殖体。为了回答这个问题,我们从12年的单种植物和混种植物中提取AMF孢子,并通过因子设计将单株AMF孢子与单株植物配对,并考察与AMF孢子来源和植物物种特性的交互作用。研究结果表明,不同植物混合种植的AMF孢子比单一栽培的AMF孢子更能成功地定植于多种植物和植株个体中。此外,我们还发现,来自不同混合种植的AMF孢子比来自单一栽培的AMF更能显著提高白车轴草(Trifolium repens L.)的生物量。与单一栽培相比,起源于不同植物混合种植的AMF孢子的生存能力和与多种植物相互作用的能力更强。我们的研究结果首次表明,多样的植物群落可以维持土壤中AMF的活力,也证明了多样的植物群落有潜力维持AMF繁殖体的活力对土壤健康和生产力至关重要。